jueves, 10 de mayo de 2012


Text and Indicated Photos: José Manuel Serrano Esparza

In a ceremony held today in Berlin, Leica has presented its new Apo-Summicron-M 50 mm f/2 ASPH, the best 50 mm lens ever made in the world, finishing with the 33 year undisputed quality supremacy as a benchmark optical design in the f/2 aperture standard focal length scope of the 1979 Summicron-M 50 mm f/2 fourth version lens (featuring identical formula than the 1994 Summicron-M 50 mm f/2 fifth version) designed by Walter Mandler without any aspherical elements and featuring a classic Double Gauss scheme stretched to its very limit.

                                 Photo: José Manuel Serrano Esparza                                           
Peter Karbe, Head of the Optical Department of Leica Camera AG at Solms, has been the optical designer of this new 50 mm f/2 flagship, which at the same time attains something that was deemed in the frontier of the physically and scientifically impossible: to beat the optical performance of the Summilux-M 50 mm f/1.4 ASPH, a true masterpiece which was till now the unchallenged king in the 50 mm standard lens sphere, from which it follows that the new Apo-Summicron-M 50 mm f/2 ASPH is now the best Leica M lens of all time, becoming the worldwide qualitative benchmark from the very moment of its presentation.


It´s an 8 elements in 5 groups design, featuring an aspherical surface, three elements made with anomalous chromatic dispersion glass and two with high refractive index glasses.

These optical glasses boasting exceedingly high performance have been manufactured by the Leitz Laboratory of Research of Optical Glasses, the international diacronic benchmark in its speciality and that from a historical viewpoint was the first creating highly refractive and thorium free lanthanum optical glass, as well as being the pioneer in the design and making of the first machine to polish and grind aspherical elements with utmost accuracy and setting up a production line.

On the other hand, the optical scheme of this Apo-Summicron-M 50 mm f/2 ASPH provides the best of two worlds:

a) Three optical elements with a clear Double-Gauss configuration (above all the first and third beginning from the left of the diagram, very similar in their shape - though with a larger degree of curvature and a much bigger building construction-  to the elements 1 and 3 of the front area beyond the diaphragm of Walter Mandler´s 6 elements in 4 groups Summicron-M 50 mm f/2 Fourth Version ( in this case, the element 2 located between both of them is much thicker and with much lesser degree of curvature than the element 2 of the front area of Apo-Summicron-M 50 mm f/2 ASPH ) .

b) Five optical elements - of which one, the nearest to the diaphragm, is an aspherical one- located behind the blades and inspired by the arrangement of the five back optical elements of the Summilux-M 35 mm f/1.4 ASPH, working as an optical floating group and enabling to attain the maximum feasible image quality from the minimum focusing distance of 0.7 m up to infinite.

Nevertheless, the aspherical element of the Apo-Summicron-M 50 mm f/2 ASPH has an even bigger width and curvature than the aspherical lens of the Summilux-M 35 mm f/1.4 ASPH, a difference in width and curvature that is much larger in the four elements placed behind the aspherical lens of the Apo-Summicron-M 50 mm f/2 ASPH, which feature a remarkable size and have undoubtedly been made with the most exclusive Leitz optical glasses -indicated in the image with thick dots-

able to provide the necessary properties to fulfill such a colossal optical tour de force and at the same time to keep as light a weight as possible.

On the other hand, Leica has also used in this design very specially formulated and expensive glues, outstanding because of their impressive adherence and preservation of their qualities throughout decades, which can be mainly seen in the four elements located behind the aspherical surface of the Apo-Summicron-M 50 mm f/2 ASPH, cemented in groups of two, and whose dimensions are much bigger than the other four elements of its optical formula.

It´s an optical design of absolutely extreme level of difficulty, in which Leica tackles the challenge of not only creating a 50 mm f/2 aspherical lens greatly beating Mandler´s Summicron-M 50 mm f/2 Version 4 (dating back to 1979), but above all of even outpeforming the Summilux-M 50 mm f/1.4 ASPH at f/2, f/2.8 and f/5.6 apertures, something which was thought to be almost impossible until very recently.

And Peter Karbe has achieved it through a masterful synergy between the Double-Gauss design stretched to its very limit according to the parameters Über die Berechnung einfacher Gauss-Objective set forth by Walter Mandler in his doctoral dissertation at Giessen University (Germany) in 1979 for the elements of the front part of the objective, and the optical scheme of the Summilux-M 35 mm f/1.4 ASPH featuring nine elements (with five of them after the diaphragm working as a global floating element, and of which the elements 6, 7, 8 and 9 are cemented in groups of two) for the back part of the optical cell behind diaphragm, managing to get the final design in 8 elements (Leica always endeavours to design their lenses with the least possible number of elements, weight, volume and diameter), when there was also the choice of following the scheme of Summilux-M 50 mm f/1.4 ASPH, sporting 8 elements in 5 groups in the same way as the Apo-Summicron-M 50 mm f/2 ASPH, but with only two of them (7 and 8) operating as a floating elements. 

All of it has been made with a clear aim: trying to create a 50 mm lens as near as possible to the unfeasible concept of 100% perfect objective, with a stellar image quality at every f stop and focal range, both in the center and border and corners, with an unprecedented uniformity of performance between f/2 and f/5.6.

If we add to it that as well as beating the Summilux-M 50 mm f/1.4 ASPH from f/2 on, which was deemed almost impossible, Leica has managed to reduce the length (47 mm), diameter (53 mm) and weight (300 g) as to such an extraordinary lens (52.5 mm in length, 53.5 mm in diameter and a weight of 335 g), the magnitude of the optical and mechanical feat can begin to be properly understood.

That´s to say, Leica has put in the new best in the world 50 mm lens just presented in Berlin all of its huge experience and know-how in the design of photographic lenses, adding to the evolutive Double-Gauss zenith achieved by Mandler (three front elements of the Apo-Summicron-M 50 mm f/2 ASPH located beyond the diaphragm) the most advanced and state-of-the-art technology of aspherical surfaces started in early nineties by the Office of Design of Leica Camera AG directed by Lothar Kölsch with a great team in which were Horst Schröder, Peter Karbe, Sigrun Kammans and others, and that after around twenty years of development, Peter Karbe has taken to its limit (five back elements of Apo-Summicron-M 50 mm f/2 ASPH placed behind the diaphragm blades).


Leica has always paid very thorough attention to the mechanical components of its lenses, made of noble metals like aluminum and brass (which are given the adequate surface treatment to avoid corrosion) along with a number of high-tech stainless-steel springs, screws and diaphragm blades, and in this regard, the construction of the Apo-Summicron-M 50 mm f/2 ASPH must undoubtedly match the amazing image quality it renders, because however good a lens may be, it will only give its full potential featuring a mechanical precision and optics assembly on a par with imaging performance. Only that way it is possible to avoid a progressive loss of qualities with the elapse of time.

And this is an exceedingly substantial side often forgotten when speaking about top-notch lenses, since to all intents and purposes the mechanical quality is as important as the optical one.

Leica lenses are created to flawlessly keep their 100% integral properties throughout a lot of decades of hard professional work under every kind of photographic assignment and weather condition, even the most extreme, so both the glasses and the mechanical parts must undergo preliminary hard tests before being delivered for manufacture, during which a high production uniformity is assured with very tight tolerances, to such an extent that a mathematical pattern generates optical systems by means of the combination of individual lens elements during the mounting stage, also making up for tolerances errors which could happen during the manufacturing.

In this regard, the grinding and polishing of the highly curved element 3 of the front part of the Apo-Summicron-M 50 mm f/2 ASPH must have required a tremendously accurate and delicate work, in the same way as the aspherical surface of the element 5, just behind the diaphragm, and with the added difficulty of placing it exactly at the distance necessary to interact with the first of the four big elements - with difference the largest ones of the eight inside the optical cell - located very near it, so a lot of different tests will have been made with this new flagship lens making use of measuring instruments created for each check and being computer assisted to get both the required spacings and an utterly exact alignment of every center of curvature on the optical axis.

Needless to say that difficulties will have been of geometric magnitude to accurately adjust and assemble those big elements 5, 6, 7 and 8 (cemented in two groups of two lenses each one) estimating the expansions and contractions which could have an effect on them, in order to attain the exceedingly stringent Leica quality standards and tolerances. And to achieve it, those big individual lens elements stuck into lens groups must be assembled onto metal mounts, in the same way as the individual lens elements.

On the other hand, I think that there´s a high probability that each Apo-Summicron-M 50 mm f/2 ASPH will have been subjected to around 100 very hard test criteria, among them maybe including temperature shocks between approximately -30º C and + 30º C, to which must be added the very substantial fact that the helical focusing mount, the bayonet, the iris diaphragm and the rest of lens mount components are designed with fairly painstaking care on a big computer screen and using a computer assisted design program, after which the exceedingly accurate manufacture begins on state-of-the-art CNC controlled machines.

The MTF curves provided by Leica Camera AG clearly prove that they don´t make any hype at all when they state that the Apo-Summicron-M 50 mm f/2 ASPH is a milestone in the History of Optical Design which has expanded the limits of the technically possible to set new standards in picture quality in 35 mm digital photography.

It is the pure truth:
                  Apo-Summicron-M 50 mm f/2 ASPH at full aperture f/2

                           Apo-Summicron-M 50 mm f/2 ASPH at f/2.8

                             Apo-Summicron-M 50 mm f/2 ASPH at f/5.6



The Summicron-M 50 mm f/2 5th Version (with an optical formula designed by Walter Mandler in 1979 in its 4th Version), which has been in production since 1994, will go on being manufactured, which is in my viewpoint a very wise decision by Leica, that this way offers along with the new world flagship Apo-Summicron-M 50 mm f/2 ASPH and the extraordinary Summilux-M 50 mm f/1.4 ASPH a cheaper choice in the scope of standard 50 mm focal focal length objectives, lacking aspherical surfaces but boasting a virtually unbeatable compactness and weight lightness, as well as keeping on providing an image quality that albeit not being so syperlative as the one delivered by the other two more expensive aspherical 50 mm Leica M lenses, is still excellent.

Walter Mandler´s Summicron-M 50 mm f/2 5th Version (launched into market in 1994) with identical optical formula than the Summicron-M 50 mm f/2 4th Version (launched into market in 1979), with the only difference that the most modern version features an extendable built-in hood. Photo: José Manuel Serrano Esparza

Chromed Summicron-M 50 mm f/2 5th Version with its built-in hood in extended position.

Back view of Summicron-M 50 mm f/2 5th Version with the 6-bit coding for use with Leica M9, M9-P and Leica Monochrom. Photo: José Manuel Serrano Esparza

Left diagonal back view of Summicron-M 50 mm f/2 5th Version. Photo: José Manuel Serrano Esparza

Summicron-M 50 mm f/2 5th Version on a Leica M9-P. The compactness, low weight and ability to exceedingly comfortable handheld shooting of this tiny and very beautiful lens with any Leica M camera are unique, along with its proved potential to get superb image quality even at maximum aperture f/2.
                  Photo: José Manuel Serrano Esparza

Front view of Summicron-M 50 mm f/2 4th Version. Photo: José Manuel Serrano Esparza

Not in vain, this little jewel is a world class lens and has been the flagship of 35 mm format f/2 lenses for 33 years, being prominent not only because of its top-notch optical performance, but also due to its building quality,

Back diagonal view of Summicron-M 50 mm f/2 4th Version. Photo: José Manuel Serrano Esparza

Diagonal lateral view of Summicron-M 50 mm f/2 4th Version. Photo: José Manuel Serrano Esparza

Lateral view of Summicron-M 50 mm f/2 4th Version. Photo: José Manuel Serrano Esparza

with a mechanizing of metallic components, of grinding and polishing of optical elements, of coating of surfaces and of their mounting inside the objective barrel according to manual craftmanship guide lines which were clearly betokened from early fifties by true masters like Ernst Hasenaier, Ernst Pausch and Hans Karl Wiese, whose labour would be followed from the beginning of nineties - with more updated methods, ultramodern machines and use of computers - by experts in the field of assembling of optical elements like Rainer Schnabel, Stefan Schlünz, Ulrich Schröder and others.

                                Photo: José Manuel Serrano Esparza

To shoot handheld with a Leica M9, M9-P or Leica Monochrom connected to a Summicron-M 50 mm f/2 lens is a real relish, besides making up a minimalist conceived photographic equipment, yet sporting a great portability, outstanding handling easiness, a practical obliteration of trepidation and a maximum f/2 aperture enabling to tackle most real photographic contexts which can arise, with the invaluable help of digital full frame sensors, that render much more quality of image in high isos than analogue cameras.

Summicron-M 50 mm f2 4th Version leaning on its tab. Photo: José Manuel Serrano Esparza

Copyright Text and Indicated Photos: José Manuel Serrano Esparza. LHSA